A tyre comprises a toroidal body ply turned up about two beads and supporting a tread. A tread belt, normally comprising a number of superimposed tread plies, is interposed between the body ply and the tread. And each bead comprises a number of metal cords embedded in elastomer to form a so-called bead bundle, and is fitted with a bead filler made of tough elastomer to increase the rigidity of the sidewalls of the tyre, and which has a triangular cross section, with its base resting on the bead.
As described, for example, in Patent Application EP0310417A2, each bead filler is normally fitted to the corresponding bead before building the tyre, i.e. the two beads, together with the bead fillers, are placed on the body ply laid flat about the building drum, prior to the turn-up operation.
The main purpose of the bead filler is to ensure a continuous variation in the elastic response of the relatively rigid bead materials and the relatively elastic sidewalls of the tyre. The presence of the bead filler, however, has a negative effect on the mass, and therefore the rolling performance, of the tyre, both directly, on account of the mass of the bead filler itself, and indirectly, by requiring relatively wide turn-up portions of the body ply.
One of the ways most commonly adopted to improve tyre performance is to reduce the overall mass of the tyre. That is, given the relatively high speed at which the tyre rotates in use, reducing its mass also brings about a corresponding reduction in rotation-related mechanical inertia.
Patent application EP2239130A1 discloses a tyre building method, in which two beads are placed on top of the body ply, between the body ply and each bead is placed, flat, an elastomer ring, and then the body ply is turned up about the two beads to form two turn-ups, each at least partly enclosing a bead, and to U-fold each elastomer ring about the bead to bring two opposite ends of the elastomer ring into close proximity.
Patent application DE102008049315A1 discloses a tyre, in which each bead filler is at least partly enclosed inside a turn-up of the body ply and has an elastomer ring, which is placed between the body ply and the bead and is turned up about the bead to bring two opposite ends of the elastomer ring into close proximity so that the two opposite ends are connected each to the other by curing.